# How to get first value of an array with condition

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Sharah 2018 年 7 月 11 日

I need to get the first value of a matrix (x2 below) that I initially put condition to, for example:
x1 = Data{i}.Error(something == 1, 1)
x2 = x1(1)
I need to do this within one step without creating `x1', is it possible? Obviously
Data{i}.Error(something == 1, 1)(1)
won't work

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### 採用された回答

Adam Danz 2018 年 7 月 11 日

By using the 2nd input to find() you can get just the first index of 'Error'.
% fake data
Data{1}.Error = magic(10);
something = [0 1 0 1 0 1 0 0 0 0];
% 2-line method
x1 = Data{1}.Error(something == 1, 1);
x2 = x1(1);
% 1-line method
x3 = Data{1}.Error(find(something == 1, 1), 1);
% Check that they match
x2 == x3
Note that this works if x2 is always the first element of x1. If you're looking for the n_th element of x1 you'll need to replace find() with
max(find(something == 1), n).

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